The LISA1 experiment is a test of in-situ tritium release. Conducted in the SILOE reactor at CEN Grenoble, the experiment uses the same facilities as the LILA1. The experiment has six capsules, four with Li 2 SiO 3 , one with Li 4 SiO 4 and one with LiAlO 2 . Each capsule is separately purged. The tritium activity is determined by ionization chambers and scintillation counting. An important difference as compared to LILA1 is the use of zinc beds to reduce tritiated water and thereby prevent sorption of T 2 O on the lines. Irradiation began on October 25, 1985 and was continued for three 3-week-cycles. The testing included systematic variation of four parameters: temperature (450 to 730°C), neutron flux (0.8 to 2.7 × 10 17 m −2 s −1 ), sweep gas flow rate (1.8 to 7.0 1/h), and sweep gas composition (He, He+0.1% H 2 , He+0.2% 0 2 ). Preliminary results are given.

Several in-pile irradiation experiments on samples of lithium aluminate provide tritium retention and release data. Such as for all tritium breeders, the interpretation of results is not straightforward. All the results are not explained if only the kinetic contributions to the tritium inventory, diffusion or mass transfer resistance at the solid-gas interface, are considered. In particular, it is necessary to consider tritium adsorption at grain surfaces in order to explain that, at higher temperatures, small grain samples have a higher tritium inventory than samples with large grains. However, at lower temperatures, tritium retention is lower with smaller grains, and above 450°C and with the addition of hydrogen to the sweep gas, the tritium residence time is less than one day. Some nonreproducibility in the results shows that parameters playing a role in the tritium release are not all clearly identified. A more accurate characterization of the surface state of the samples is required.

Performance of HTR fuel particles is examined by irradiation experiments in Material Test Reactors. An important goal is the determination of particle failure fraction during irradiation. To do this a nondestructive method was developed to ensure zero failure at the begin of the irradiation test. The fueled samples are activated for half an hour in an electrically heated furnace in reactor Melusine. The resulting fission gases are trapped and quantitatively evaluated. From the resulting R/B-values the number of failed particles can be deduced. In two test series with a total number of 24 fuel compacts no defective particle could be found. Detection limit R/B Kr 85 m was 10−8.